Belly spends the summer of her sixteenth birthday transitioning from childhood into young adulthood. She wants to feel grown up and experience her first love, but she’s still clinging to the innocence of childhood. Although her father initially gave her the nickname “Belly” because Isabel sounded too mature for a child, it comes to hint at the womanly curves she has developed as she’s grown.
Belly matures emotionally and physically over the course of the summer. She is self-involved at the start of the novel, obsessing over her crush on Conrad and using her growing relationship with Cam to make him jealous. As the story progresses, Belly matures, becoming more empathetic toward those around her and refocusing her attention on supporting her loved ones.